This invention relates to power plants and more particularly, it concerns improvements in variable displacement reciprocating engines, principally internal combustion engines which operate in accordance with the well-known Otto or Diesel cycles, but also including heat engines in which fuel is burned externally, such as steam engines and Stirling engines, for example.
In a co-pending application for U.S. Patent, Ser. No. 738,704, filed Nov. 3, 1976 by the present inventor, there is disclosed an embodiment of an internal combustion engine in which power developed by pistons reciprocating in cylindrical combustion chambers is transmitted to a nutating generally cylindrical member carried by an external rotary support member about an output shaft having a pair of oppositely convergent cone-like members to which torque is transmitted by friction from internal rolling surfaces on the cylindrical nutating member. The thrust of piston reciprocation is absorbed by double-ended swivel links each having one end universally pivotal about a fixed point of reference and the other end universally pivotal in a socket fixed at one end of the nutating cylindrical member. A feature of the illustrative embodiment disclosed is the provision of an eccentric sleeve means by which the angle of cylindrical member nutation may be varied in a manner to vary the length of piston stroke relative to a cylinder head either with or without a constant compression ratio.
In such engines, the frequency of piston reciprocation is directly proportional to the angular velocity of the support journaled to the exterior of the cylindrical nutating member. Output speed or angular velocity of the shaft to which the cone-like members are keyed is a function of the effective internal radius of the nutating cylindrical member and the radii of the cone-like members at the point of frictional engagement between these members. Output speed may be varied for a given engine speed by shifting a pair of ring-like members carried on the interior of the cylindrical nutating member axially of the cone-like members carried on the output shaft.
In an engine of this type, the rotational speed of the output shaft is related to engine speed in accordance with the following equation: EQU .omega. = .alpha. - .alpha.R.sub.1 /R.sub.2
in the operation, .omega. represents the rotational or angular velocity of the output shaft; .alpha. is the rotational velocity of the nutating member support about the axis of the output shaft or the orbital velocity of the nutational axis in a bi-conical path about the output shaft axis; R.sub.1 is the radius of the effective internal rolling surface of the nutating member; and R.sub.2 is the radius of each cone-like member at the point of frictional engagement with the respective internal rolling surfaces of the nutating member.
From the above formula, it will be appreciated that output velocity (.omega.) will be equal to engine speed (.alpha.) but in a direction of rotation opposite to engine speed when the proportion R.sub.1 /R.sub.2 = 2. Also, this condition will exist when the angle of intersection between the axis of the nutating member and the output shaft axis is maximum. For a given engine speed (.alpha.), the speed of output shaft rotation will decrease to or approach zero as the ratio R.sub.1 /R.sub.2 approaches one. Because the internal rolling surfaces carried by the nutating members are provided on axially shiftable ring-like members, the ratio of output speed to input speed may be varied independently of the angle of axes intersection though in a manner requiring excessive axial movement of the nutating member carred rings as a result of varying the angle of nutating member axis intersection with the axis of the cone-like members to alter the length of piston stroke of the engine.
In addition, it is well known that the power developed by piston-type internal combustion engines varies directly with length of piston stroke or displacement and frequency of piston reciprocation or engine speed. In an engine of the type referred to above, therefore, where piston stroke varies directly with variation in the angle of intersection between the axis of the nutating member and the axis of the cone-like members, it would be desirable to achieve an operating condition in which output shaft speed and engine speed are varied in inverse proportion to variation of piston stroke length or engine displacement. Under such conditions, developed power can be controlled to optimize engine efficiency for varying loads connected to the output shaft.